Manual and self-adjusting heating-electrode structure for dielectric heating



Feb. 28, 1950 w. H. ANDERSON ETAL 2,498,632

. MANUAL AND SELF-ADJUSTING HEATING-ELECTRODE STRUCTURE FOR DIELECTRIC HEATING 2 Sheets-Sheet 1 Filed April 28, 1948 Fig? 5 50 347 Q am; a

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W. H. ANDERSON ET AL MANUAL AND SELF-ADJUSTING HEATING-ELECTRODE STRUCTURE FOR DIELECTRIC HEATING w a My WWW Feb. 28, 1950 Filed April 28, 1948 Patented Feb. 28, 1950 UNITED STATES PATENT OFFICE MANUAL AND SELF-ADJUSTING HEATING- ELECTRODE STRUCTURE FOR DIELEC- TRIC HEATING Application April 28, 1948, Serial No. 23,794

31 Claims. 1

Our invention relates, broadly, to dielectric heating apparatus, and more particularly to a supporting structure for the heating-electrodes thereof.

In the use of small dielectric heating units, one or more objects to be heat-treated are placed between a pair of relatively insulated heatingelectrodes which is carried directly by the unit, the unit also containing the electronic tubes and high-frequency circuits which generate the high-frequency electrical energy supplied to the heating-electrodes.

The heating-electrodes are usually two small parallel plates arranged one above the other. In order to prevent high-frequency radiation and to provide apparatus in which a dielectric object can be quickly and safely heat-treated and then replaced by another object to be heattreated and for other reasons, the heating-electrodes are commonly enclosed or surrounded by a two-member metallic cage which carries one of them. One of the cage-members is relatively movable with respect to the other for opening and closing the cage so that work can be readily loaded into the open cage, heated while the cage is closed, and then unloaded.

In prior cages of this type, the heating-electrodes were restricted as to flexibility of adjustment for heating objects or work of different heights and under different conditions.

A purpose or object of our invention is to make a small portable self-contained dielectric heating unit of a type described more universal by building itso that it can successively heat a plurality of objects with the upper heating-electrode pressing heavily on each object, or resting more lightly on each object, or spaced from the top of each object so as to provide an air space thereabove. To this end we provide a heating-electrode struc ture of a type described which is both manually and automatically adjustable. Slight variations in the heights of objects manufactured on a mass production basis as a single batch are automatically taken care or by the supporting means for one of the heating-electrodes. Wide differences in the heights of objects of different batches are accommodated by manual adjustments.

A further purpose of our invention is to provide an adjustable heating-electrode structure of Q accommodated without attention from the operator.

A more particular purpose of our invention is to provide a cage-structure for dielectric heating units of a type described, the cage-structure having a raisable member which fioatingly supports an upper heating-electrode in any desired position with in the cage. This heating-electrode can be adjusted through a comparatively wide range without altering its axial alignment with ithe cooperating lower heating-electrode upon which an object rests for heat-treatment by the high-frequency electric field between the heating-electrodes.

Specifically we achieve the foregoing and other objects of our invention by providing a cage member which carries one end of a pantographic linkage that is movable in a vertical plane. The other end of the linkage floatingly carries an upper heating-electrode. A stop is provided which prevents the heating-electrode from dropping below a predetermined point which may be at or near the top of the object to be heat-treated. However, by lowering the supported end of the linkage, the upper heating-electrode can be made to press more firmly on the top of the object being heat-treated; and by raising the supported end any desired air gap or separation can be provided between the upper heating-electrode and the object. In the preferred embodiment of our invention herein described, the cage-member which carries the pantographic linkage and upper heating-electrode is hinged to the other cage-member and is movable. In another embodiment shown in the copending W. H. Anderson application, Serial No. 139,547, filed January 20, 1950, a stationary cage-member adjustably carries the pantographic linkage.

In accordance with the preferred embodiment herein described, the hinged cage-member has wall-means that extends above the other casemember. This wall-means carries an adjustable support or end member to which an end of the pantographic linkage is pivotally attached. By adjusting the support vertically, the position of such end of the linkage is changed correspondingly. Specifically, the support means includes a threaded member which can be turned from outside the cage in order to make the desired adjustments for placing the upper heating-elem trode that is carried by the pantographic linkage in desired relation to the work on the lower heating-electrode.

Further features, innovations and combinations of our invention, in addition to the foregoing, will b discernible from the following description of a preferred embodiment thereof which is to be taken in conjunction with the accompanying drawings. Several figures of the drawings are drawn on different. scales, but each figure has its parts drawn to scale. In the drawings:

Figure 1 is a vertical sectional view of a dielectric heating unit embodying our invention, the solid lines showing the operating position of the cage of the unit when an'obJ'ect is heattreated with an air gap above it, and the broken lines showing the raised position of a part of the cage;

Fig. 2 is a plan view of a linkage arrangement inside the cage, which floatingly supports the upper heating-electrode;

Fig. 3 is a front elevational view of the apparatus of Fig. 2, the front being at the left of Fi 2;

Figs. 4 and 5 are vertical sectional views substantially on the lines IVIV and V-V, respectively, of Fig. 2; and

Fig. 6 is a partially vertical sectional view of apparatus embodying our invention, but adjusted to have the upper heating-electrode press on the top of an object to be heat-treated.

Referring more particularly to Fig. l, a top wall 2 very sketchily represents the outer metallic casing of a high-frequency generating unit that includes equipment, within the casing, for generating high-frequency power. A suitable circuit for delivering the power includes an insulated conductor 4 which passes. centrally through an insulating bushing 8 in the top wall 2 and is connected to a lower heatingeelectrode 8 carried by the bushing.

The other side of the circuit is connected to a second upper heating-electrode H] which is above the heating-electrode B. The connection can be made in any suitable manner, such as, for example, by solidly grounding both the heating-electrode iii and the associated side of the energizing circuit to the casing of the generator unit. Accordingly, a pair .of heating-electrodes is provided, one above the .other, which are relatively insulated. Such heating-electrodes usually, but not necessarily, comprise fiat metal plates having a, square, circular or other contour.

The upper heatingelectrode it is supported by a pantographic linkage indicated in its entirety by the reference numeral 52. The linkage isin turn carried from a supporting frame which encloses or surrounds the heating-electrodes 8 and IE3 and the pantograph linkage i2.

As shown in Fig. 1, the supporting frame comprises the top wall '2 and a metal cage-structure of more or less conventional form. The cagestructure comprises a lower member l6 fixed to the top wall 2 and an upper raisable member it which is movable with respect to the lower member.

In a horizontal cross section of the preferred embodiment shown in the drawings, to which our invention is obviously not limited, the cagemembers it and i8 appear rectangular. The walls of the cage-members are apertured for ventilation, an apertured section being indicated at 29. The cage-members l6 and G8 are hinged together by a hinge 22 along the back side of the cage. Preferably the hinge 2 2 is of a type that can automatically retain the cage-member H3 in a raised position, such as shown in the broken lines of Fig. 1, without the help of an operator; but can be readily released and lowered by an d operator. A counterweight can be provided if desired for balancing the weight of the cagemember l8 about the hinge 22.

The joint between the two cage-members i6 and i8 slopes downwardly to the front so as to provide an extensive front wall on the movable cage-member I8. Preferably this joint is electrically sealed; and to this end, the joint is formed of nestable lips 24 and 26, one of which frictionally carries for its full length, a springy channel 28 that slidably engages the other, as more particularly described in our application Serial No. 51,246, filed September 25, 1948.

The upper cage-member i8 is raisable through a handle Bil on its front wall. Opening of the cage operates a switch 32 for preventing the application of electrical power across the heating-electrodes 8 and I0. Closing of the cage restores the switch 32 to normal so that power can again be applied to the heating-electrodes.

The front wall of the cage-member I8 is providedwith a relatively large rectangularly dished portion 34 within which an upright lead screw 36 is carried for rotational, but not for axial, movement. The lead screw 38 had one end projecting through the top of the cage-member it for receiving a handle 38 for turning the lead screw. A releasable tightening nut 49 can be Screwed tightly against the top of the cagemember for locking the lead screw against ac- Cidental rotation.

The raisable cage-member l8 adjustably carries the pantographic linkage l2 through the lead screw 36, so that the last constitutes, in effect, a sup-port member for the lead screw. The pantographic linkage comprises a bar or end member which forms an end of the linkage and is indicated in. its entirety by the reference numeral 42. As shown more particularly in Figs. 2 and 3, the bar member 52 comprises a backwardly extending bar it having a central threaded hole receiving the lead screw 36, and a pair of horizontal bars A l extending laterally from the lateral vertical sides of the bar 43. The far ends of the bars 45 have projections 45 which slide along or are very close to'the adjacent parts of the dished portion .34 of the front wall of the cage member 18 so as to keep the pantographic linkage l2 in aligned position for different adjustments on the lead screw 35. Accordingly, this dished portion ad is in the nature of a guide ffOI the pantographic linkage as the latter is raised or lowered by the lead screw 36.

Referring also to Figs. 2-5, the bar 43 of the carriage or bar member 42 comprises a comparative thick plate which extends backwardly from the lead screw 35. This rearward portion of the bar l3 carries the rest of the pantographic linkage. To this end, it is provided with vertically aligned holes adapted to receive journals, or the equivalent, for a lower pivot it and an upper pivot .67. The lower pivot 36 is longer than the upper pivot 41. Lower links 58' and 48" are secured to opposite ends of the lower pivot 45; and upper links 50 and 5d" are secured to opposite ends of the upper pivot ll. Accordingly, the portion of the bar 43 between the pivot t6 and 4? also constitutes a vertical link or rod for the pantographic linkage 52, this link or rod being integral with the portion of the bar member 32 that engages the lead screw 36. Since the group of links d3, 58', 5t and to" extend generally horizontally away from the vertical link of the pantographic'linkage 12 provided by the bar 453, the said group of links can be generally designated as horizontal links although it should be understood that in operation they will assume positions which are not absolutely level but may be at a considerable angle to a line which is absolutely horizontal. Accordingly, it should be understood that the term "horizontal as used in connection with the links embraces more than a direction at 90 to an absolutely vertical line.

More specific details of the manner in which the horizontal links are pivotally supported from the bar 43 are shown in Fig. 5. The bar 43 has a horizontal lower hole and a horizontal upper hole for the pivots 4B and 41, respectively. Bearing 52 is fixed in the lower hole and extends outwardly therefrom. The pivot 46 comprises a short shaft which rotates in this bearing. The front ends of the links 48 and 48 are fixed to this shaft by bolt-means 54 and 56 so as to swing together. The upper pivot 41 comprises a through-bolt journalled in a bearing 51 fixed in the upper hole of the bar 43. The front ends of the links 50' and 50" are fixed to the bolt by a nut and washer means 58 so that these parts also swing as they group.

The joint-acting lower links 48' and 48" and th joint-acting upper links 50' and 50 are parallel and extend backwardly to a pair of rear pivots 60 and 62 respectively, to which they are fixed by bolt and nut means 64 and 66, respectively. The lower pivot 60 and the upper pivot 62 are rotatably carried, in a suitable manner, in lower and upper horizontal superimposed holes in a bar 68.

The bar 68 extends downwardly below the pivots 60 and 62 and has a portion to which the metal plate of the upper heating-electrode It] is secured so that the bar 68 and the heatingelectrode l0 move as a single group or unit. Hence the bar 68 can be considered to be a unitary part of the heating-electrode l0; and its portion between the pivots B0 and 62 can be considered to be an end link or rod of the pantographic linkage [2, which link or rod is carried by the heating-electrode In.

From the foregoing, it is apparent that the pantographic linkage comprises the first bar or end member 42 at one end, the horizontal links 48, 48", 50 and a second end member at the other end, comprising 50", and the vertical bar 68 at such other end. One end of the linkage that including the bar 42is adjustably carried by the lead screw 36. The other end of the linkage fioatingly carries the heating-electrode In. In order to provide greater lateral rigidity to the linkage so as to prevent it from weaving from side to side, the intermediate portions of the lower links 48 and 48" are provided with an integral crosspiece 12.

One of the swingable links, more particularly the lower link 48', has an angle bar 14 secured to its front end. This angle bar 14 projects in a direction toward the lead screw 36 and is adapted to abut a stop screw 16 which is threaded in a hole in a guide piece 44 of the carriage or bar member 42. The angle bar 14 o the linkage l2, and the stop screw 16 on the bar member 42, form a stop means which limits downward movement of the linkage by the weight of the linkage, the heating-electrode H) or other force. The stop screw 16 is adjustable and preferably it is adjusted so that the swingable links 48, 4B", 59 and 50" and also the heating-electrode [0 will be substantially level in operative position during heat-treatments.

In order to use the apparatus with the heating-electrode l0 pressing downwardly on an object to be heat-treated, the upper links 50' and 50" have lugs 18 projecting laterally outwardly therefrom at a point backwardly of the upper pivot 41. These lugs 18 receive ends of tension springs 80. The other ends of the springs are wrapped around the bearing 52 so that, in effect, ends of the springs are anchored to the carriage or bar member 43 in all positions of this bar member. The anchored ends of the springs are also relatively stationary with respect to any fixed position of the lead screw 36 and the cagemember 18. The springs constitute a forceexerting device which tends to move the upper links 50 and 50" clockwise about the upper pivot 41, as viewed in Fig. 1. This means that the whole pantographic linkage and the heatingelectrode i0 will also tend to move clockwise until the abutment-stop angle bar 14 reaches the stop screw 16, or until further clockwise movement of the linkage is prevented by resistance of an object for heat-treatment in centact with the lower side of the heating-electrode It Turing the handle 38 of the lead screw 36 moves the heating-electrode it] up or down in a rectilinear direction, without changing the axial alignment of the two heating-electrodcs 8 and I 0; and a considerable variation in the spac ing between the heating-electrodes can be thus obtained.

In each particular adjustment of the lead screw 36, objects of different heights can be successively heat-treated without further turning of the lead screw 36, provided their heights do not vary more than the distance in which the free end of the pantographic linkage It can tilt upwardly. Greater variations in the heights of objects can be taken care of by turning the lead screw. Two typical operating positions of the apparatus are shown in Figs. 1 and 6. In Fig. 1, an article W can be heat-treated with an air gap between it and the heating-electrode I 0. The pantographic linkage is in its lowermost position with respect to the stop screw 16, and While in this position, it can be raised or lowered to provide the desired air gap.

Fig. 6 shows an operating position of the apparatus for heat-treating an object NV with the upper heating-electrode in resting on or press ing on the top surface of the object. For such operation, the bar member 43 is first dropped by rotating the handle 38 until the heating-electrode Ill rests on the top of the object W, and the linkage l2 tilts relatively upwardly on the bar 43 so that the stop screw it separates from the angle bar I4 a distance which will allow for the maximum variation in the heights of other similar objects to be heat-treated. By further lowering the bar member 43 to another relatively lower operating position, the pressure of the heating-electrode IE! on the object W will be increased. In this lower operating position, the heating-electrode It will exert a force on the object W which depends on the weight of the heating-electrode Hi, the weight of the linkage l2, and the tension on the springs 39 which may be as much as or little as desired.

From the foregoing, it is obvious that by rais-- ing and lowering the pantographic linkage 52, a plurality of articles of considerably different heights can be successfully heat-treated with or without an air gap and with or without pressure being applied to the top surfaces of the objects.

ll While we have described our invention in a preferred form, it should be obvious to one skilled in the art that its teachings can be applied to other embodiments and forms so that our invention is not necessarily limited to the modifications herein described.

We claim as our invention:

1. A dielectric heating unit of a type described comprising, in combination, a cage having a relatively stationary member and a raisable member, a pair of relatively insulated heatingelectrodes in said cage, a first of said heatingelectrodes being above the second of said heating-electrodes, and a pantographic linkage in said cage having horizontal links tiltable up and down, said horizontal links being connected by end members, said linkage having an end secured to said first heating-electrode and its other end carried by said raisable cage-member.

2. A dielectric heating unit of a type described comprising, in combination, a cage having a relatively stationary member and a raisable member, a pair of relatively insulated heating-electrodes in said cage, a first of said heating-electrodes being above a second of said heating-electrodes, a pantographic linkage in said cage having horizontal links tiltable up and down, said horizontal links being connected by end members, said linkage having an end secured to said first heating-electrode, and an adjustin means carried by said raisable cage-member for adjustably carrying the other end of said pantographic linkage. v

3. An invention including that of claim 2 but characterized further by a stop means for limiting tilting of said horizontal links. 7

4. A dielectric heating unit of a type described comprising, in combination, a cage having a relatively stationary member and a raisable member, a pair of relatively insulated heating-electrodes in said cage, a first of said heating-electrodes being above a second of said heating-electrodes, a pantographic linkage in said cage having horizontal links tiltable up and down, and end members connecting said links, one of said end members carrying said first heating-electrode, an adjusting means carried by said raisable cage-member for adjustably carrying the other end member of said pantographic linkage, and a spring means having spring-ends connected to anchoring points on said unit, at least one of which is on said linkage, said points being separated difierent distances depending on the adjustment of said adjusting means.

5. An invention including that of claim 2 but characterized further by a stop means for limiting downward movement of said linkage.

6. A dielectric heating uniit of a type described comprising, in combination, a cage having a relatively stationary member and a raisable member, said raisable member having an upstanding wall, a pair of relatively insulated heating-electrodes in said cage, a first of said heating-electrodes being above a second of said heating-electrodes, a movable bar carrying said first heating-electrode, a pair of vertically separated horizontal links having ends pivoted to said bar, a bar member to which the other ends of said links are pivoted, and means carried by said upstanding wall of said raisable cage-member for in turn carrying said bar member.

7. A dielectric heating unit of a type described comprising, in combination, a cage having a relatively stationary member and a raisable member having an upstanding wall, a pair of relatively insulated heating-electrodes in said cage, a

first of said heating-electrodes being above a second of said heating-electrodes, a movable bar carrying said first heating-electrode, a pair of vertically separated horizontal links having ends pivoted to said bar, a bar member to which the other ends of said links are pivoted, means carried by said upstanding wall of said raisable cage-member for in turn carrying said bar member, and a spring anchored to one of said horizontal links and to said bar member.

8. A dielectric heating unit of a type described comprising, in combination, a cage having a relatively stationary member and a raisable member having an upstanding wall, a pair of relatively insulated heating-electrodes in said cage, a first of said heating-electrodes being above a second of said heating-electrodes, a movable bar carrying said first heating-electrode, a pair of vertically separated horizontal links having ends pivoted to said bar, a bar member to which the other ends of said links are pivoted, a spring anchored to one of said horizontal links and to said bar member, and means for carrying said bar member from said upstanding wall of said raisable cage-member, the last said means comprising an adjusting device for adjusting the position of said bar member with respect to said raisable cage-member.

9. A dielectric heating unit of a type described comprising, in combination, a cage having a relatively stationary member and a raisable member hinged to a side of said stationary cage-member, a pair of relatively insulated heating-electrodes in said cage, a first of said heating-electrodes being above a second of said heating-electrodes, a bar secured to said first heating-electrode, a pair of vertically separated links having ends pivoted to said bar, a bar member to which the other ends of said links are pivoted, a guide for said raisable cage-member in which said bar member can slide, and means carried by said raisable cage-member for adjustably positioning said bar member in said guide.

10. A dielectric heating unit of a type described comprising, in combination, a cage having a relatively stationary member and a raisable member, a pair of relatively insulated heating-electrodes in said cage, a first of said heating-electrodes being above a second of said heating-electrodes, an upstanding lead screw, said raisable cage-member having means rotatably supporting said lead screw, a handle device for turning said lead screw, a pantographic linkage having a member engaging said lead screw, said linkage being arranged for vertical tilting, said linkage having another member secured to said first heating-electrode.

11. A dielectric heating unit of a type described comprising, in combination, a cage having a relatively stationary member and a raisable member, a pair of relatively insulated heatingelectrodes in said cage, a first of said heatingelectrodes being above a second of said heatingelectrodes, an upstanding lead screw, said raisable cage-member having means rotatably supporting said lead screw, a handle device for turning said lead screw, a pantographic linkage having a member engaging said lead screw, said linkage being arranged for vertical tilting, said linkage having another member secured to said first heating-electrode, and a force-exerting device connected to said linkage tending to move said linkage so as to press said first heating-electrode downwardly.

12. An invention including that of claim 11 but Characterized, in addition, by a stop for limiting tilting of said linkage.

13. A dielectric heating unit of a type described comprising, in combination, a cage having a relatively stationary member and a raisable member hinged to a side of'said stationary cage-member, a pair of relatively insulated heating-electrodes in said cage, a first of said heatingelectrodes being above a second of said heatingelectrodes, a wall of said raisable cage-member having an upright portion at the side opposite the hinged portion, a lead screw rotatably carried in said upright portion, a handle carried on the outside of said cage for turning said screw, a pantographic linkage having a bar member slidable in said upright portion, said bar member engaging said screw, said linkage also comprising a pair of links pivoted to said bar member and also to said first heating-electrode.

14. Dielectric heating equipment comprising, in combination, a pair of relatively insulated heating-electrodes, a first of said heating-electrodes being above a second of said heating-electrodes, a frame and means for supporting said first electrode by said frame, said means comprising an upright support member, a bar member adjustably carried by said support member, a pair of vertically spaced horizontally extending links pivoted to said bar member, and means pivotally attaching said links to said first heatingeiectrode, and a force-exerting means for forcing said heating-electrode downwardly.

15. An invention including that of claim 14 but further characterized by a stop means for limiting downward movement of said first heatingelectrode.

16. A dielectric heating unit of a type described comprising, in combination, a cage having a relatively stationary member and a raisable member, a pair of relatively insulated heating-electrodes in said cage, a first of said heatingelectrodes being above a second of said heatingelectrodes, a pantographic linkage in said cage having horizontal links tiltable up and down, and end members connecting said horizontal links, one of said end members carrying said first heating-electrode, and an adjusting means carried by said raisable cage-member for adjusting the position of said pantographic linkage with respect to said raisable cage-member.

17. A dielectric heating unit of a type described comprising, in combination, a cage having a relatively stationary member and a raisable member, a pair of relatively insulated heating-electrodes in said cage, a first of said heatingelectrodes being above a second of said heatingelectrodes, a pantographic linkage in said cage having horizontal links tiltable up and down, and end members connecting said horizontal links, one of said end members carrying said first heating-electrode, and an adjusting means carried by said raisable cage-member for adjusting the position of said pantographic linkage with respect to said raisable cage-member, said adjusting means comprising an adjusting member above the top of said raisable member.

18. A dielectric heating unit of a type described comprising, in combination, a cage having a relatively stationary member and a raisable member, said raisable member having an upstanding wall, a pair of relatively insulated heating-electrodes in said cage, a first of said heating-electrodes being above a second of said heating-electrodes, a movable bar carrying said first heating-electrode, a pair of vertically separated horizontal links having ends pivoted to said bar, a bar member to which the other ends of said links are pivoted, and means carried by said upstanding wall of said raisable cage-member for in turn carrying said bar member, said adjusting means comprising an adjusting member outside of said raisable cage-member.

19. An invention including that of claim 8 but further characterized by said adjusting device comprising a member extending through said cage and having an adjusting member above said bar member.

20. An invention including that of claim 9 but characterized further by the last said means comprising an adjusting member on the outside of said raisable cage-member.

21. A dielectric heating unit of the type described comprising, in combination, a cage having a relatively stationary member and a relatively movable member, a pair of relatively insulated heat-electrodes in said cage, a first of said heating-electrodes being above the second of said heating-electrodes, and a pantographic linkage in said case having horizontal links tiltable up and down, said horizontal links being connected by end members, said linkage having an end secured to said first heating-electrode and its other end carried by one of said cage-members.

22. A dielectric heating unit of a type described comprising, in combination, a pair of relatively insulated heating-electrodes, a first of said heating-electrodes being above a second of said heating-electrodes, a cage about said heating-electrodes, said cage having a pair of cagemembers which are relatively movable to open and close said cage so that work to be heattreated can be placed between said heating-electrodes, a pantographic linkage in said cage carried by a first of said cage-members and having generally horizontal but tiltable links, end members connecting said links, one of said end members carrying said first heating-electrode, means associated with the second of said cage-member for carrying said second heating-electrode, and a biasing means connected to said pantographic linkage, tending to move said pantographic linkage and said first heating-electrode in a predetermined direction inside said cage.

23. A dielectric heating unit as defined in claim 22 but further characterized by said biasing means comprising a spring having an end anchored to move with said pantograpli and an end anchored so as to be substantially stationary with respect to said first cage-member, and adjusting means for adjusting the position of the last said spring-end.

24. A dielectric heating unit as defined in claim 23 but further characterized by said adjusting means for said linkage comprising an adjusting member accessible from outside of said cage when said cage is closed.

25. A dielectric heating unit of a type described comprising, in combination, a pair of relatively insulated heating-electrodes, a first of said heating-electrodes being above a second of said heating-electrodes, a cage about said heating-electrodes, said cage having a pair of cage-members which are relatively movable so that work to be heat-treated can be placed between said heatingelectrodes, a pantographic linkage in said cage carried by a first of said cage-members and having generally horizontal but tiltable links, end members connecting said links, means associated with one of said end members for carrying said first heating-electrode, means associated with the 11 other of said cage-members for carrying said second heating-electrode, and an adjusting means carried by said cage for adjusting the position of the other of said end members of said pantographic linkage and said first heating-electrode inside said cage.

26. A dielectric heating unit of a type described comprising, a pair of vertically-spaced, relatively insulated heating-electrodes, a cage surrounding said heating-electrodes, said cage comprising a pair of cage-members, one of said cage-members being relatively movable with respect to the other of said cage-members, whereby the cage can be loaded and unloaded with said work, a first of said cage-members having wall means extending above a second of said cage-members, a pantographic linkage in said cage having generally horizontal but tiltable links, end members pivotally carrying said links, one of said end members I carrying the upper of said heating-electrodes, and means associated with said wall means carrying the other of said end members.

27. A dielectric unit as defined in claim 26 but characterized further by an adjustable stop means limiting downward movement of said pantographic linkage and said upper heatingelectrode.

28. A dielectric heating unit of a type described comprising, a pair of vertically-spaced, relatively insulated heating-electrodes, a cage surrounding i,

said heating-electrodes, said cage comprising a pair of cagemembers, one of said cage-members being relatively movable with respect to the other of said cage-members, whereby the cage can be loaded and unloaded with said work, a first of said cage-members having wall means extending above a second of said cage-members, a pantographic linkage in said cage having generally horizontal but tiltable links, end members pivotally carrying said links, one of said end members carrying the upper of said heating-electrodes, means associated with said wall means carrying the other of '12 said end members, and an adjustable stop means limiting movement of said pantographic linkage and upper heating-electrode in a downward direction, said adjustable stop means comprising an adjusting member accessible from the outside of said cage when said cage-members are closed.

29. Dielectric heating means of the type described comprising a pair of vertically-spaced, relatively insulated heating electrodes adapted to receive Work therebetween, a pantographic linkage having generally horizontal but tiltable links, end members pivotally carrying said links, means associated with one of said end members for dependingly carrying the upper of said heatingelectrodes, support means or carrying the other of said end members, said pantographic linkage having biasing means tending to move said pantographic linkage and said upper heating-electrode in the predetermined direction.

30. Dielectric heating means as defined in claim 29 but further characterized by said biasing means comprising a spring having an end anchored to move with said pantographic linkage and said upper heating-electrode and an end anchored on said support means, and adjusting means for adjusting the position of the last said spring-end.

31. Dielectric heating means as defined in claim 30 but further characterized by adjustable stop means for predetermining the position of said pantographic linkage and upper heating electrode with respect to said lower heating electrode.

WILLIAM H. ANDERSON. DEAN S. SHINGLER.

REFERENCES CITED The following references are of record in the file of this patent:

A fl -kw. H. F. generator, Electronic Engineering, August 1945, page 633. 

